JP2001310387A - Heat-resistant vinyl chloride-lined steel pipe and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a heat-resistant vinyl chloride-lined steel pipe in which a heat-resistant vinyl chloride pipe and a steel pipe are hardly peeled off even when subjected to a heat history, and a method for producing the same. SOLUTION: The heat-resistant vinyl chloride pipe is a heat-resistant vinyl chloride-lined steel pipe which is heat-expanded and bonded to the inner surface of the steel pipe via an adhesive, wherein the heat-resistant vinyl chloride pipe has a softening temperature of 120 ° C or higher. And a heat-resistant vinyl chloride-lined steel pipe characterized by having a radial strain of 0.6% or less at 20 ° C. and a softening temperature of 1 in the steel pipe.
A heat-resistant vinyl chloride pipe having a temperature of 20 ° C. or higher was applied by applying an adhesive to the outer surface of the heat-resistant vinyl chloride tube or the inner surface of the steel tube or both surfaces thereof, and the steel tube was heated from the outside and inserted. The method for producing the heat-resistant vinyl chloride-lined steel pipe, wherein the heat-resistant vinyl chloride pipe is heated and expanded to be bonded to the inner surface of the steel pipe, and the time at which the temperature of the heat-resistant vinyl chloride pipe is equal to or higher than the softening temperature is 15 minutes or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heat-resistant vinyl chloride pipe used for a hot / cold water pipe used for hot water supply or air conditioning or a drain pipe through which high-temperature water flows, wherein the vinyl chloride pipe is lined by an expansion method. The present invention relates to a steel pipe and a method for manufacturing the same.

[0002]

2. Description of the Related Art Heat-resistant PVC pipes (hereinafter referred to as heat-resistant PVC)
When a heat-resistant vinyl chloride-lined steel pipe (hereinafter, referred to as a heat-resistant LP pipe) is manufactured by lining the pipe by a so-called thermal expansion method, a heat-resistant PVC pipe having a strain in a diameter reducing direction at the time of molding is used. . The diameter of this heat-resistant PVC tube expands when heated (hereinafter referred to as “heat expansion”).
When bonding a heat-resistant PVC pipe to the inner surface of a steel pipe, both the heat-resistant PVC pipe and the steel pipe are heated to a high temperature, and the heat-resistant PVC pipe is heated and expanded and adheres to the steel pipe, but is cooled to room temperature. At this time, since the coefficient of linear expansion of the heat-resistant PVC pipe is larger than that of the steel pipe, the amount of shrinkage is large, and since the pipes are joined to each other with an adhesive, a stress in a direction in which the heat-resistant PVC pipe peels off from the steel pipe remains. Therefore, when the adhesive strength decreases with time, a phenomenon occurs in which the heat-resistant PVC pipe is peeled off from the steel pipe.

[0003] When a heat-resistant LP tube is used for hot and cold water, this phenomenon tends to appear remarkably due to so-called repetitive thermal shock, and there has been a problem that various piping troubles are likely to occur.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a heat-resistant vinyl chloride-lined steel pipe manufactured by an expansion method, wherein the heat-resistant vinyl chloride pipe and the steel pipe are hardly peeled off even when subjected to a heat history. The purpose of the present invention is to provide a lining steel pipe and a method for producing the same.

[0005]

According to a first aspect of the present invention, there is provided a heat-resistant vinyl chloride-lined steel pipe (invention 1) in which a heat-resistant vinyl chloride pipe is adhered to an inner surface of the steel pipe by an expansion method. A heat-resistant vinyl chloride-lined steel pipe, wherein the heat-resistant vinyl chloride pipe has a softening temperature of 12
A heat-resistant vinyl chloride-lined steel pipe characterized by having a strain of 0 ° C. or more and a radial strain at 20 ° C. of 0.6% or less.

According to a second aspect of the present invention, there is provided a method for producing a heat-resistant vinyl chloride-lined steel pipe (invention 2), wherein a heat-resistant vinyl chloride pipe having a softening temperature of 120 ° C. or more is provided inside the steel pipe. Alternatively, an adhesive is applied to the inner surface of the steel pipe or to both sides thereof and inserted, and the steel pipe is heated from the outside, and the inserted heat-resistant vinyl chloride pipe is heated to expand and adhere to the inner surface of the steel pipe, and the heat resistance is improved. Invention 1 is a method for producing a heat-resistant vinyl chloride-lined steel pipe according to Invention 1, wherein the time during which the temperature of the vinyl chloride pipe is equal to or higher than the softening temperature is 15 minutes or less.

[0007] As steel pipes to be lined,
A carbon steel pipe for piping, a galvanized steel pipe, and the like are generally used, but are not limited thereto.

[0008] Considering the use of heat-resistant LP pipes, since abnormally high-temperature hot water may temporarily flow,
The heat-resistant PVC pipe used for the heat-resistant LP pipe of the present invention includes a softening temperature (Vicat softening temperature, JIS K 720).
6) is required to be 120 ° C. or higher. Usually, a stabilizer containing a chlorinated vinyl chloride as a main component or a polyvinyl chloride to which a known heat resistance improver is added, if necessary, It is preferable to use a product produced by extrusion-molding a mixture of materials, lubricants and the like, followed by quenching while reducing the diameter.

When such a heat-resistant PVC pipe is heated to a softening temperature or more at the time of lining processing, expansion deformation starts, and when the diameter is expanded to the inner wall of the steel pipe at a certain temperature, further expansion cannot be performed. Is strongly pressed against the inner wall of the steel pipe, and the heat-resistant PVC pipe and the steel pipe are bonded to each other. Thus, at least above this temperature, the adhesive must flow.

As the adhesive, any of a solvent type, a water emulsion type and a hot melt type may be used. However, in many cases, a hot melt type adhesive is used from the viewpoint of sanitary environment and workability. As the composition of the adhesive, a known adhesive such as a polyester resin, a modified polyethylene resin, an ethylene-vinyl acetate copolymer resin, and a styrene-butadiene copolymer resin may be used.

When the heat-resistant PVC pipe is bonded to the steel pipe by heating, the heat-resistant LP pipe is cooled to room temperature. The stress in the direction in which the diameter contracts remains in the heat-resistant PVC pipe at room temperature after cooling due to the difference between the coefficient of thermal expansion of the heat-resistant PVC pipe and that of the steel pipe. That is, internal strain remains, which causes peeling between the heat-resistant PVC pipe and the steel pipe due to repeated thermal shock applied by the supply of hot water.

This phenomenon is caused by the fact that the adhesive force reduced by the influence of the hot water becomes smaller than the peeling force caused by the residual strain. If the original residual strain of the heat-resistant PVC pipe is small, the hot water While the adhesive force is reduced by the influence, the residual strain is also relaxed and reduced by heat, and no peeling occurs. However, the residual strain ε used in the present invention is the difference d between the inner diameter Di of the steel pipe at 20 ° C., the outer diameter Do of the heat-resistant PVC pipe including the adhesive thickness when the steel pipe is extracted from the steel pipe, and the inner diameter Di of the steel pipe. Is calculated from the following equation.
Residual strain ε = (difference d / inner diameter of steel pipe Di) × 100 (%)

If the ε at 20 ° C. is 0.6% or less, even if the thermal shock is repeatedly applied for a long time by hot water, the heat-resistant PVC pipe and the steel pipe do not peel off. That is, in Invention 1, the heat-resistant PVC pipe has a softening temperature of 120.
By using a resin having a residual strain ε ≦ 0.6% at 20 ° C. or higher, a heat-resistant LP tube that does not peel off for a long period of time is obtained.

The condition of ε ≦ 0.6% can be achieved by reducing the total amount of heat applied to the heat-resistant PVC pipe in the lining process in the production of the heat-resistant LP pipe. The heating temperature during the lining process must be high enough to ensure that the heat-resistant PVC pipe expands and adheres tightly to the inner surface of the smooth steel pipe.
The heating time at a temperature equal to or higher than the softening temperature of the tube may be reduced, and the time is within 15 minutes.

The shorter this time is, the smaller the residual strain is. This is a heat-resistant PVC with heat expansion properties.
The tube has the ability to expand beyond the inner diameter of the steel tube by heating, but it is presumed that this is due to the fact that the shorter the time of exposure to the high temperature, the larger the shape, the larger the shape. Here, the heating temperature of the heat-resistant PVC tube means an average value when the outer surface temperature and the inner surface temperature of the heat-resistant PVC tube are measured by a thermocouple.

[0016] The heating furnace used in the lining processing step is to adjust the temperature of the heat-resistant PVC pipe inserted in the steel pipe to the heat-resistant PV pipe.
Any type may be used as long as the outer diameter of the C pipe expands beyond the inner diameter of the steel pipe and heating can be performed to a temperature higher than the temperature at which the adhesive is activated. For example, as an example, a heating heat source that uses hot air or infrared or high-frequency induction heating or the like may be used. As a furnace type, a V-shaped heating furnace that sequentially heats from the center of the tube toward both ends thereof, An I-shaped heating furnace for sequentially heating one end of the tube from one end to the other end may be used. Regardless of the type of heating furnace, if a cooling device for rapidly cooling the lining steel pipe coming out of the heating furnace is installed, the time during which the temperature of the heat-resistant PVC pipe is equal to or higher than the softening temperature is adjusted. This is convenient because it is easy to do.

(Operation) As described above, in the first aspect,
Softening temperature of 120 ° C or higher and 20 ° C as a heat-resistant PVC tube
By using the residual strain ε ≦ 0.6% in
The result is a heat-resistant LP tube that does not peel off over a long period of time.

According to the second aspect of the present invention, the heat-resistant P
Since the heating time at or above the softening temperature of the VC tube is 15 minutes or less, it is possible to obtain a heat-resistant LP tube in which a heat-resistant PVC tube having a residual strain ε of 0.6% or less is used as an inner layer tube.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the heat-resistant vinyl chloride-lined steel pipe of the present invention and a method for producing the same will be described in detail with reference to examples.

Example 1 A polyester hot-melt adhesive (flow starting temperature 125 ° C.) was attached to the outer surface of a chlorinated vinyl chloride pipe (outer diameter 50.7 mm, wall thickness 3.0 mm, softening temperature 125 ° C.) as a heat-resistant PVC pipe. C.) was applied to a thickness of 100 μm using an extrusion crosshead mold, and inserted into a carbon steel pipe for piping (nominal diameter 50 A, outer diameter 60.5 mm, wall thickness 3.8 mm). The heat-resistant PVC pipe is provided with thermal expansion so that the outer diameter at 160 ° C. becomes 58.0 mm.

As a heating furnace for the lining process, FIG.
The steel pipe 2 into which the heat-resistant PVC pipe 3 is inserted is sequentially moved from the top T of the V-shape using the hot-air blowing type V-shaped heating furnace H shown in FIG. The heat-resistant PVC pipe 3 was bonded to the steel pipe 2 by heating to obtain a heat-resistant LP pipe 1. At this time, the final surface temperature of the heat-resistant PVC pipe 3 is 1
The moving speed was adjusted so that the time when the temperature reached 60 ° C. and the heating temperature became 125 ° C. or higher was 10 minutes. The heated and lined pipe 1 is immediately cooled and cooled.
In order to shorten the time of 5 ° C. or more, cooling air is blown by the air nozzle A onto the surface of the steel pipe 2 immediately after leaving the V-shaped heating furnace H to cool.

The residual strain of the heat-resistant PVC tube of the obtained heat-resistant LP tube is 0.4%, and hot water of 95 ° C. is heated at 20 ° C. for 10 minutes.
Was passed through for 20 minutes, and this was repeated 3000 times to apply a thermal shock, but no separation between the heat-resistant PVC pipe and the steel pipe was observed.

The same heat-resistant LP as in Example 1 was used, except that the same material as in Example 1 was used, and the heating conditions in the lining process were changed to 125 ° C. or higher for 20 minutes.
I got a tube.

The residual strain of the heat-resistant PVC pipe of this heat-resistant LP pipe is 1.0%, and hot water at 95 ° C. is passed through for 10 minutes and water at 20 ° C. for 20 minutes. , Peeling between the heat-resistant PVC pipe and the steel pipe was observed.

[0025]

As described above, in the heat-resistant vinyl chloride-lined steel pipe obtained by the production method of the present invention, the heat-resistant vinyl chloride pipe and the steel pipe are hardly peeled off even when subjected to a heat history.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an example of an apparatus for producing a heat-resistant polyvinyl chloride pipe.

[Explanation of symbols]

 Reference Signs List 1 Heat-resistant vinyl chloride-lined steel pipe (heat-resistant LP pipe) 2 Steel pipe 3 Heat-resistant vinyl chloride pipe (heat-resistant PVC pipe) H Hot air blowing type V-shaped heating furnace T Heating furnace tip A Air nozzle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 705: 12 B29K 705: 12 B29L 23:00 B29L 23:00

Claims (2)

[Claims] 1. A heat-resistant vinyl chloride-lined steel pipe having a heat-resistant vinyl chloride pipe bonded to an inner surface of a steel pipe by an expansion method, wherein the heat-resistant vinyl chloride pipe has a softening temperature of 120 ° C.
And the radial strain at 20 ° C. is 0.6
% Or less, a heat-resistant vinyl chloride-lined steel pipe. 2. A heat resistant vinyl chloride pipe having a softening temperature of 120 ° C. or more is inserted into a steel pipe by applying an adhesive to the outer surface of the heat resistant vinyl chloride pipe, the inner surface of the steel pipe, or both surfaces thereof. The steel pipe is heated from the outside, the inserted heat-resistant vinyl chloride pipe is heated and expanded and adhered to the inner surface of the steel pipe, and the time when the temperature of the heat-resistant vinyl chloride pipe is higher than the softening temperature is 15 minutes or less. The method for producing a heat-resistant vinyl chloride-lined steel pipe according to claim 1, wherein